The present invention relates to cleaning of gases produced by a combustion engine from solid and/or liquid particles suspended therein. Gases of this kind are both combustion gases leaving the engine through its ordinary exhaust pipe and, for instance, so-called crankcase gases, i.e. combustion gases released through the crankcase of the engine, to which they have been pressed from the engine cylinders past the piston rings of the engine pistons.
Crankcase gases have to be released so that they do not create an all too high gas pressure in the crankcase, and they contain in addition to combustion products, such as soot particles, also an amount of oil drops entrained from the oil mist having been formed and being present in the crankcase during the operation of the combustion engine.
For cleaning of gases of this kind various types of devices have been suggested previously, by means of which the gases may be brought into a rotational movement, so that the particles suspended in the gases may be separated by centrifugal force. Thus, it has been suggested that the gases should flow through a cyclone having one or more tangential inlets for the gases or flow through a chamber of a stationary housing, in which they are caused to rotate by means of a central driving wheel provided with wings or other entrainment members, e.g. as can be seen from U.S. Pat. No. 1,950,586 or DE 43 11 906 A1. Furthermore, it has been suggested that the gases should flow through channels or a separation chamber within a rotating member driven in one way or another by means of the combustion engine. According to one suggestion a rotating member of this kind would be driven by means of some rotating part of the combustion engine, as shown for instance in EP 0 736 673 A1, DE 196 07 919 A1 and U.S. Pat. No. 4,329,968. According to another suggestion the rotating member would be driven by means of kinetic energy of the gases which have been produced by the combustion engine and which are to be cleaned, as shown for instance in GB 1 465 820 and DE 35 41 204 A1.
The above-mentioned suggestions for cleaning of gases having been produced by a combustion engine each having one or more drawbacks. Thus, the suggestions based on the gases being caused to flow through a chamber formed by a stationary housing and being caused to rotate therein by means of a driving wheel or the like, which is provided with wings or similar entrainment members, have the disadvantage that a sufficiently effective separating operation is difficult or impossible to accomplish by means of this kind of technique. The suggestions being based on use of a rotatable member, which within itself forms a separation chamber through which the gases are to flow, have the disadvantage that the suggested methods of operating such a rotatable member either are difficult to use, if a very large rotational speed is desired for the rotating member, or put certain demands on the physical location of the rotatable member. It is often a desire that it should be possible to locate an equipment for cleaning of gases from a combustion engine at a desired place at or at a distance from the combustion engine.
A starting point of the present invention for cleaning of gases of the kind here in question is the use of a rotatable centrifugal rotor, which forms and surrounds a separation chamber, through which the gases should be brought to flow. Only by means of a centrifugal rotor of this kind a sufficiently effective cleaning of the gases is achievable. An object of the invention is to accomplish driving of said centrifugal rotor in a way which enables, in a simple manner, both that a very high rotational speed can be achieved and that the centrifugal rotor can be located at a desired place near the combustion engine.
According to the invention it is proposed for the fulfillment of this object a method of cleaning gases, having been produced by a combustion engine, from solid and/or liquid particles suspended therein, which method thus takes as a starting point in that the gases are conducted through a separation chamber formed and surrounded by a rotating member, by means of which the gases are brought to rotate, so that the particles are separated from the gases in the separation chamber by means of centrifugal force, and which method is characterised in that the combustion engine is used to generate a pressure fluid other than that constituted by exhaust gases pressurised in the combustion room of the combustion engine, and that this pressure fluid is used for the driving of the rotating member.
By the method according to the invention it is achieved, firstly, that an effective centrifugal separator can be used, in which a centrifugal rotor can be driven by means of pressure fluid at a very high rotational speed and, secondly, that a centrifugal rotor of this kindxe2x80x94as a consequence of the fact that it is drivable by means of a pressure fluid which can be simply conducted to any desired placexe2x80x94can be arranged in a best possible space within or in the vicinity of the combustion engine.
Normally, a combustion engine pressurises for its own need fluids of different kinds. For instance fuel, lubricating oil and cooling water are pressurised. This is accomplished by means of pumps which in one way or another are operated by means of energy from the combustion engine. Furthermore, in certain cases the air, which has to be supplied to the combustion room of the engine, is pressurised by means of a compressor. Normally, this is driven by the exhaust gases leaving the combustion engine.
According to various modifications of the invention fluids having been pressurised in manners like this may be used for operation of the rotatable member in the aforementioned separator. The operation of the rotatable member may be accomplished by means of a turbine wheel or a similar member, which is connectedxe2x80x94directly or through a gear devicexe2x80x94with the rotatable member of the separator. An operation of this kind can be accomplished independently of whether the pressurised fluid is constituted by a liquid or a gas. The driving can be accomplished alternatively by means of a hydraulic or pneumatic motor of one kind or another.
One way of driving the rotatable member is to conduct all or part of the pressurised fluid into a rotatable housing, which is directlyxe2x80x94or indirectly through a gear devicexe2x80x94connected with the rotatable member, at least part of the fluid being caused to leave the housing through an outlet that is directed and placed such in relation to a rotational axis, around which the housing is rotatable, that the fluid leaving through the outlet will bring the housing and said rotatable member into rotation. This driving method can be used independently of whether the pressure fluid is constituted by a gas or a liquid.
Particularly in connection with diesel engines it is common that lubricating oil is cleaned by causing a part flow of the lubricating oil, which is pumped to relevant lubricating places in the engine, to pass through a so-called reaction-driven centrifugal separator. A centrifugal separator of this kind has a rotor, in which pressurised lubricating oil is introduced, one or several outlets for lubricating oil leaving the rotor being so placed and directed that the rotor, as a consequence of the outflow of lubricating oil, is brought and kept in rotation. According to a particular application of the invention, a centrifugal separator of this kind for lubricating oil may be used for driving of the rotatable member in the aforementioned separator for cleaning of gases from the combustion engine. Thus, this rotating member may be carried by or be driven in some suitable way by the rotor in the centrifugal separator for lubricating oil.
It is of course possible within the scope of the present invention to use the combustion engine for pressurisation of a fluid, which is intended solely for the operation of said rotatable member or, at least, is not intended for any other need of the combustion engine. Thus, the combustion engine may be adapted for operation of an electric generator, electricity from this electric generator being used for pressurisation of a fluid. For instance, an electrically driven compressor for pressurisation of air, intended for operation of said rotatable member, may be coupled to an electric generator of this kind.
The invention also concerns a plant for performing the above described method of cleaning gases which have been produced by a combustion engine.
A plant of this kind comprises a centrifugal separator having a rotor, which is rotatable around a rotational axis and which delimits and surrounds a separation chamber, and gas conducting members for conducting said gases from the combustion engine into the rotor separation chamber, so that they are caused to rotate therein. The plant is characterised in that the combustion engine is adapted for operation of a pressurisation device for generating a pressure fluid other than that constituted by exhaust gases pressurised in the combustion room of the combustion engine, that the centrifugal separator has a driving device for said rotor, which driving device is adapted to cause rotation of the rotor by means of a pressure fluid, and that pressure fluid conducting members are adapted to conduct pressure fluid from said pressurising device to said driving device for rotation of the rotor.